The present invention relates to a de-icer for removing unwanted material from objects, and relates more particularly to an electro-expulsive blanket for shattering and removing ice and other fungible material from an accreting surface such as that of an airfoil.
Presently, electro-expulsive blankets are used to remove ice from certain areas of airfoils most vulnerable to ice accretion. For instance, electro-expulsive blankets typically cover an exposed or leading edge of a plane's airfoil. These blankets typically comprise an elastomeric outer layer having a lower surface attached to the outer surface of an airfoil to be protected from ice accretion and having an upper or ice-accretion surface exposed to the elements. Within the blanket are two layers of conductor windings that when electrically energized repel one another so as to cause the accretion surface of the blanket to move outwardly and rapidly away from the relatively stationary lower surface. The stretched and outwardly moving accretion surface of the outer elastomeric layer combines with a restoring spring within the blanket to generate a restoring force to decelerate the accretion surface's outward movement. The rapid deceleration of the ice-accretion surface shatters and removes any accumulated ice which is bonded to the accretion surface.
One drawback with using elastomeric outer-layer blankets is that the shedding efficiency (Watts per unit area shed) is relatively low as compared to stiffer materials, such as composite fabrics. A second drawback is that the shedding efficiency of elastomeric blankets is reduced by the limited non-linearity of conventionally used restoring springs located within the blanket. A third drawback with elastomeric blankets is a short operational life because of the relatively low erosion resistance of elastomeric materials as compared to composite fabrics.
Accordingly, it is a general object of the present invention to provide an electro-expulsive blanket with a composite fabric outer layer for improved shedding efficiency and erosion resistance over that of blankets using conventional elastomeric outer layers.
It is another object of the present invention to provide a novel inner restoring force from within the composite fabric blanket to further improve shedding efficiency.
It is a further object of the present invention to provide slits through the composite fabric outer layer to limit damaging hoop stress which arises when the relatively stiff composite fabric blanket is fired.